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Re: [CPROG] pointer gymnastik



Thomas M. wrote:
> Hejsa

Hej!

> Jeg har en streng på x antal bytes,som "abcdefg..xyzABCDEFG..XYZ123..890"
> Jeg vil gerne finde ud af index'et på et bestemt tegn 'B' f.eks. Problemet
> er at index() returnerer en pointer til tegnet, i stedet for en index ind
> i strengen (som f.eks. at B er nr. 29. tegn i strengen). Hvordan for jeg
> lige omregnet dette til et brugbart index? (bruger det til at indexere med
> ind i strengen igen med chars[indx])

Hmm.. Jeg maa indroemme at jeg ikke kan huske en stdlibc funktion til at
koerer noejagtigt dette (proev dog at kigge paa strstr()), men dette
burde virke (maaske en smule langsomt):

int lookupChar(const char *str, char c)
{
  char *p;
  int i;

  for (p = str, i = 0; *p != '\0'; *p++, i++)
  {
    if (*p == c)
      return i;
  }

  return -1;
}

> Thomas Mørch

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| Per Vognsen (Randers - Denmark)| "Superstition is a  word the |
| Mail: <sslug@sslug>   | ignorant  use   to  describe |
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